Using species distribution models and termal tolerance traits to investigate nicheconservatism in an invasive mite

De Mendoza CONICET

Few studies have explicitly investigated physiological traits of an invasive species in both its native and invasive ranges. The
redlegged earth mite, Halotydeus destructor, provides an exciting opportunity to test niche conservatism across ranges. The
species is a major agricultural pest in Australia, having arrived from South Africa nearly 100 years ago. Over the last 40
years the invasive range has exhibited an inland expansion to hotter and drier conditions. Species distribution models built
on South African and Australian datasets show that the niche of the native range is unable to be projected to the extent of
the invasive range. The models also reveal an apparent shift in climatic variable importance between native and invasive
distributions and that in Australia, different variables presently limit (e.g. aridity) the inland range expansion than historically
(e.g. winter rainfall). These results lead to hypotheses concerning an adaptive shift in the fundamental niche of H. destructor.
Thermal tolerance traits such as critical thermal maxima and minima (CTmax & CTmin) strongly relate to the fundamental
niche in terrestrial arthropods. Guided by our models, we tested for thermal tolerance differences in populations of H.
destructor across an environmental gradient in Australia. We also measured native populations in South Africa to test for
conservatism of thermal tolerance traits. The results help understand niche conservatism in invasive species and also feed
into a predictive framework to better understand how future climate change may influence the distribution of this important
pest species.